Structural and Electrical conductivity of Mn doped Hematite (α-Fe2O3) phase

We investigate the structural and transport properties of Mn doped hematite (α-Fe2O3). The X-ray diffraction pattern identifies the single-phase and corundum (Al2O3) type structure of the polycrystalline samples Fe2−xMnxO3 (x = 0, 0.01, 0.10 and 0.50). The resistivity curve shows a Morin transition (TM) in hematite (α-Fe2O3) at about 262 K. As the Mn-content increases in the solid solution of hematite (α-Fe2O3), the number of pairs of (Fe2+, Fe3+) and (Mn2+, Mn3+) in the solid solution increases which changes the conductivity of the solid solution. The Mn doping influences the Morin transition and TM shifts towards lower temperatures on enhanced doping. For higher doping, TM is further suppressed significantly. The Raman measurements of α-Fe2O3 samples shows seven Raman active modes at A1g(1) ≅ 225 cm−1, Eg(1) ≅ 249 cm−1, Eg(2) ≅ 292 cm−1, Eg(3) ≅ 297 cm−1, Eg(4) ≅ 409 cm−1, Eg(5) ≅ 496 cm−1, and A1g(2) ≅ 609 cm−1. Mössbauer spectroscopy probes the site preference of the substitutions and their effect on the hyperfine magnetic fields clearly show the presence of ferric (Fe3+) state and strong magnetic ordering in all samples.

► Fe2−xMnxO4 hematites are in single phase and possess corundum type structure.
► Resistivity data shows Morin transition for parent -Fe2O3 observed at TM 262 K.
► Mn doping influences Morin transition and TM shifts towards lower temperatures.
► Seven Raman active modes are identified for Mn2+ doped Fe2−xMnxO4 hematites.
► Room temperature Mössbauer spectrum confirms +3 oxidation state of Fe as ferric.